Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 040831 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 331 AM EST Sun Dec 4 2016 .SYNOPSIS...
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A weak wave of low pressure moving along the coast will bring increasing rain chances through tonight. A more significant and complex low pressure system will move in the vicinity late Monday and Tuesday accompanied by periods of heavy rain. 2 to 3 inches of rainfall is forecast through Tuesday. Seasonable weather will follow for mid-week before an arctic front brings very cold temperatures Friday and into the weekend.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 300 AM Sunday...Sprinkles or very light rain were ongoing across the forecast area. This rain was falling out of mid clouds, but was enough to wet the ground. Measurable rain has fallen in some areas. Chilly high pressure will be moving offshore tonight. A front will extend from low pressure along the Gulf Coast eastward and will develop to our S and offshore along the Carolina coast tonight. A wave of low pressure is expected to develop along the front to our S and move NE along the Carolina coast. This will allow precipitable water values to increase through the day with the lowest levels of the column becoming saturated by/during this evening. The best isentropic lift arrives late tonight and this is when we expect the highest rainfall rates. We will show POPs increasing through the day with widespread rain expected tonight. Cloudy skies through the period will minimize the diurnal range with highs in the upper 40s to lower 50s and mid 50s along portions of the immediate coast. Lows will be mainly in the mid and upper 40s with upper 40s to around 50 near the coast.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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As of 300 AM Sunday...Rain should be temporarily tapering off from W to E, in both coverage and intensity on Monday. A frontal boundary will be draped to our S Monday and extend up the Carolina coast across the coastal waters. A wave of low pressure will be positioned on this front. The low is expected to be along the Carolina coast in the morning, lifting away from the area and shoving the front further S and E during the day. As this occurs, upward vertical motion will greatly diminish as will the depth and magnitude of moisture. We do not think the warm sector will bleed onto land Monday morning, thus any thunderstorms will be kept offshore. The main area of low pressure along the western Gulf Coast Monday will lift NE across the mid south Monday night and up the Ohio Valley Tuesday. This low pressure will actually fill/weaken late Tuesday and Tuesday night as the upper support wanes and energy is transfered to developing low pressure along the coast of North Carolina and Virginia. The primary low early Wednesday morning will be off the Del-Mar-Va. The front to our S is expected to advance N as a warm front Monday night and Tuesday as a 50 to 60 kt low level jet impinges on the area. Moisture depth increases dramatically and precipitable water values climb to near 2 inches. Strong isentropic upglide will increase rainfall rates and we expect periods of heavy rain late Monday night into Tuesday. Also, we have added mention of thunderstorms for portions of the area, especially near the coast and southern portions of the forecast area where instability increases with the arrival of the warm sector. Current timing would suggest the first half of Tuesday will be wetter than the second half. The risk for rain will end by/during Tuesday night as low pressure and its associated frontal system moves away from the area, allowing drier air in make inroads. Storm total rainfall is expected to be in the 2 to 3 inch range. A good soaking and given the time of year, we should expect low-lying areas to experience ponding despite several weeks of mainly dry weather.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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As of 300 AM Sunday...Big story this period will be a true arctic front progged to cross the Carolinas during Thursday. Ahead of this feature, dry and seasonable weather is expected as a diffuse pressure gradient sets up behind Tuesday`s cold front. Highs Wed/Thu will be in the 60s, but these will crash down with the arctic front late Thursday. 850mb temps are forecast to fall as low as -10C across this area by Friday morning, indicative of the coldest air mass we have seen since last winter. Moist advection ahead of this front is weak, but a few showers cannot be ruled out late Thursday along the front. These will all be of the liquid variety however, no snow showers this time around despite soundings forecasting dendritic saturation, as any snowflakes will sublimate into the very dry air below 700mb. Highs behind this front will drop to 15 degrees below climo Fri/Sat with lows in the 20s by Saturday morning.
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&& .AVIATION /09Z SUNDAY THROUGH THURSDAY/... As of 06Z...High pressure remains in place across the southeast centered from near the Great Lakes, but is slowly being displaced to the northeast by low pressure developing near the Gulf Coast. SW flow atop this high pressure is creating some light rain showers tonight, and periods of very light rain without any vsby restrictions are possible at FLO/LBT before daybreak. The coastal terminals are expected to remain mostly dry, although a very brief sprinkle is possible. Cigs will be VFR and winds will be light from the NE. After daybreak conditions will slowly deteriorate as NE winds increase to around 10 kts, and rainfall becomes more widespread, especially during the evening. This will cause cigs to lower through the day, and vsbys will gradually become MVFR. The combination of increasing rainfall intensity and column saturation will create IFR at all terminals, and once IFR develops it is expected to remain in place well beyond the current valid period. Extended Outlook...Periods of IFR likely through Tuesday night. MVFR developing Wed. VFR Thur. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... As of 900 PM Saturday...High pressure centered across the Ohio Valley will move eastward into the central Appalachians by early Saturday morning. This should maintain north-northeasterly wind across the coastal waters at 10-15 knots, strongest late tonight. Seas are generally 1-2 feet inside 10 miles from shore, 2-3 feet from 10-20 miles from shore. Little change is anticipated through the night. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 PM Saturday...A complex weather situation will develop Sunday into Monday. High pressure across the Mid-Atlantic states Sunday morning will weaken as a wave of low pressure along the Gulf Coast helps sharpen a coastal trough along the Carolina Coast. This trough is expected to move onshore as a warm front Sunday night, then back offshore before daybreak Monday as the low pressure area moves up the boundary and to our east. Although the strongest winds associated with this first wave should remain offshore, winds could still reach 20 knots late Sunday afternoon into Sunday night over the coastal waters, accompanied by seas building to 4-6 feet within 20 miles of shore. The front will sink a couple hundred miles to our south Monday, but Monday night a second wave of low pressure should begin to take shape to our west. This will again tug on the front, causing the boundary to approach to within 20 miles of the coast by early Tuesday morning. Winds may increase to 25 knots Monday night with seas eclipsing 6 feet. Model confidence in this scenario is building, although the precise location of the coastal front is not yet known. LONG TERM /WEDNESDAY THROUGH THURSDAY/... As of 300 AM Sunday...Cold front offshore Wednesday morning will leave winds of 10-15 kts from the NW across the waters. These winds will gradually ease through Wednesday as the gradient relaxes, and begin to back to the west into Thursday morning ahead of an arctic front. Seas Wednesday of 3-5 ft very early will fall to 2-3 ft through the day. A very strong arctic front will then cross the waters on Thursday, causing winds to veer again to the NW and increase to 15-25 kts late, pushing seas back to 2-4 ft, lowest near- shore. Attm forecast conditions are just below any cautionary thresholds, but a SCEC or SCA may be needed late Thursday if winds increase a bit more than current forecasts suggest.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...RJD SHORT TERM...RJD LONG TERM...JDW AVIATION...JDW MARINE...RJD/TRA/JDW

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